These lines relate to the themes of love and honor, or, more accurately, to love and honor deferred.
In act 4, scene 1, Benedick confesses his love for Beatrice, and she confesses her love for him. To prove his love, Benedick swears to Beatrice that he'll challenge Claudio to a duel for dishonoring Hero on her wedding day.
BENEDICK. Come, bid me do anything for thee.
BEATRICE. Kill Claudio.
BENEDICK. Ha! not for the wide world!
BEATRICE. You kill me to deny it. Farewell. ...
BENEDICK. Think you in your soul the Count Claudio hath wronged Hero?
BEATRICE. Yea, as sure is I have a thought or a soul.
BENEDICK. Enough, I am engaged, I will challenge him. I will kiss your hand, and so I leave you. By this hand, Claudio shall render me a dear account. (4.1.297-300, 333-338)
In act 5, scene 1, Claudio and Don Pedro have a confrontation with Leonato and Antonio regarding Claudio's behavior at the wedding. Leonato and Antonio exit, and Benedick enters just as Claudio and Don Pedro were about to look for him to cheer them up.
Don Pedro tells Benedick that he and Claudio were almost involved in a fight with Leonato and Antonio. Benedick remarks that there's no honor in an argument based on lies and deception.
BENEDICK. In a false quarrel there is no true valour. I came to seek you both. (5.1.124-125)
Benedick has come to challenge Claudio to a duel, as he promised Beatrice he would, but Claudio and Don Pedro think Benedick is making a joke, and they banter with him.
CLAUDIO. We have been up and down to seek thee; for we are high-proof melancholy, and would fain have it beaten away. Wilt thou use thy wit? (5.1.126-128)
Benedick is in no mood to banter. He grows increasingly angry and tells Claudio to change the subject and get serious.
BENEDICK. It is in my scabbard. Shall I draw it? ...
DON PEDRO. As I am an honest man, he looks pale. Art thou sick or angry?
CLAUDIO. What, courage, man! What though care killed a cat, thou hast mettle enough in thee to kill care.
BENEDICK. Sir, I shall meet your wit in the career an you charge it against me. I pray you choose another subject. (5.1.129, 134-139)
Don Pedro finally realizes that Benedick is serious about his challenge to Claudio.
DON PEDRO. By this light, he changes more and more. I think he be angry indeed. (5.1.142-143)
As the scene continues, Claudio still thinks that Benedick is joking, until Benedick takes him aside and issues his challenge directly and unequivocally.
BENEDICK. (Aside to Claudio) You are a villain. I jest not; I will make it good how you dare, with what you dare, and when you dare. Do me right, or I will protest your cowardice. You have killed a sweet lady, and her death shall fall heavy on you. Let me hear from you. (5.1.147-151)